[Qemu-devel] Re: [PATCH 08/15] xen: Read and write the state of the VM in xenstore

[Anthony Liguori <anthony@codemonkey.ws>]

On 08/12/2010 09:09 AM, stefano.stabellini@eu.citrix.com wrote:
> From: Anthony PERARD<anthony.perard@citrix.com>
>
> Introduce functions to read and write the state of the VM in xenstore.
>    

This basically creates a new management interface for QEMU via the xenstore.

Our management interface is QMP.  If you want to maintain compatibility, 
you'll need to write a QMP -> xenstore daemon that maps events 
appropriately.

Regards,

Anthony Liguori

> Signed-off-by: Anthony PERARD<anthony.perard@citrix.com>
> Signed-off-by: Stefano Stabellini<stefano.stabellini@eu.citrix.com>
> ---
>   hw/xen_machine_fv.c   |    9 ++++
>   target-xen/helper.c   |    7 +++
>   target-xen/qemu-xen.h |    3 +
>   target-xen/xenstore.c |  128 +++++++++++++++++++++++++++++++++++++++++++++++++
>   target-xen/xenstore.h |    6 ++
>   5 files changed, 153 insertions(+), 0 deletions(-)
>
> diff --git a/hw/xen_machine_fv.c b/hw/xen_machine_fv.c
> index ec826e7..a6e778a 100644
> --- a/hw/xen_machine_fv.c
> +++ b/hw/xen_machine_fv.c
> @@ -36,10 +36,17 @@
>   #include "xen_backend.h"
>   #include "xenstore.h"
>   #include "xen_platform.h"
> +#include "qemu-xen.h"
>   #include "xen/hvm/hvm_info_table.h"
>
>   #define MAX_IDE_BUS 2
>
> +static void xen_vm_change_state_handler(void *opaque, int running, int reason)
> +{
> +    if (running)
> +        xen_main_loop_prepare();
> +}
> +
>   static void xen_init_fv(ram_addr_t ram_size,
>                           const char *boot_device,
>                           const char *kernel_filename,
> @@ -150,6 +157,8 @@ static void xen_init_fv(ram_addr_t ram_size,
>       }
>
>       pc_pci_device_init(pci_bus);
> +
> +    qemu_add_vm_change_state_handler(xen_vm_change_state_handler, NULL);
>   }
>
>   static QEMUMachine xenfv_machine = {
> diff --git a/target-xen/helper.c b/target-xen/helper.c
> index d588e64..8cb7771 100644
> --- a/target-xen/helper.c
> +++ b/target-xen/helper.c
> @@ -19,6 +19,8 @@
>    */
>
>   #include "cpu.h"
> +#include "qemu-xen.h"
> +#include "xenstore.h"
>
>   CPUXenState *cpu_xen_init(const char *cpu_model)
>   {
> @@ -67,3 +69,8 @@ target_phys_addr_t cpu_get_phys_page_debug(CPUState *env, target_ulong addr)
>   {
>       return addr;
>   }
> +
> +void xen_main_loop_prepare(void)
> +{
> +    xenstore_record_dm_state("running");
> +}
> diff --git a/target-xen/qemu-xen.h b/target-xen/qemu-xen.h
> index d1910d6..091ae07 100644
> --- a/target-xen/qemu-xen.h
> +++ b/target-xen/qemu-xen.h
> @@ -27,4 +27,7 @@ int cpu_register_io_memory_fixed(int io_index,
>                              CPUWriteMemoryFunc * const *mem_write,
>                              void *opaque);
>
> +/* target-xen/helper.c */
> +void xen_main_loop_prepare(void);
> +
>   #endif /*QEMU_XEN_H*/
> diff --git a/target-xen/xenstore.c b/target-xen/xenstore.c
> index 9f2e1ea..6eb6a30 100644
> --- a/target-xen/xenstore.c
> +++ b/target-xen/xenstore.c
> @@ -13,6 +13,60 @@ static void xenstore_process_event(void *opaque)
>       free(vec);
>   }
>
> +static const char *xenstore_get_guest_uuid(void)
> +{
> +    static char *already_computed = NULL;
> +
> +    char *domain_path = NULL, *vm_path = NULL, *vm_value = NULL, *p = NULL;
> +    unsigned int len;
> +
> +    if (already_computed)
> +        return already_computed;
> +
> +    if (xen_xc == NULL)
> +        return NULL;
> +
> +    domain_path = xs_get_domain_path(xenstore, xen_domid);
> +    if (domain_path == NULL) {
> +        fprintf(stderr, "xs_get_domain_path() error. domid %d.\n", xen_domid);
> +        goto out;
> +    }
> +
> +    if (asprintf(&vm_path, "%s/vm", domain_path) == -1) {
> +        fprintf(stderr, "xenstore_get_guest_uuid(): out of memory.\n");
> +        goto out;
> +    }
> +    vm_value = xs_read(xenstore, XBT_NULL, vm_path,&len);
> +    if (vm_value == NULL) {
> +        fprintf(stderr, "xs_read(): uuid get error. %s.\n", vm_path);
> +        goto out;
> +    }
> +
> +    if (strtok(vm_value, "/") == NULL) {
> +        fprintf(stderr, "failed to parse guest uuid\n");
> +        goto out;
> +    }
> +    p = strtok(NULL, "/");
> +    if (p == NULL) {
> +        fprintf(stderr, "failed to parse guest uuid\n");
> +        goto out;
> +    }
> +
> +    if (asprintf(&already_computed, "%s", p) == -1) {
> +        fprintf(stderr, "xenstore_get_guest_uuid(): out of memory.\n");
> +        goto out;
> +    }
> +
> +    fprintf(stderr, "Guest uuid = %s\n", already_computed);
> +
> +out:
> +    free(domain_path);
> +    free(vm_path);
> +    free(vm_value);
> +
> +    return already_computed;
> +}
> +
>   int xen_dm_init(void)
>   {
>       xenstore = xs_daemon_open();
> @@ -29,6 +83,7 @@ int xen_dm_init(void)
>           xen_be_printf(NULL, 0, "can't open xen interface\n");
>           goto err;
>       }
> +
>       return 0;
>
>   err:
> @@ -38,3 +93,76 @@ err:
>
>       return -1;
>   }
> +
> +static char *xenstore_vm_key_path(int domid, const char *key) {
> +    const char *uuid;
> +    char *buf = NULL;
> +
> +    if (xenstore == NULL)
> +        return NULL;
> +
> +    uuid = xenstore_get_guest_uuid();
> +    if (!uuid)
> +        return NULL;
> +
> +    if (asprintf(&buf, "/vm/%s/%s", uuid, key) == -1)
> +        return NULL;
> +
> +    return buf;
> +}
> +
> +char *xenstore_vm_read(int domid, const char *key, unsigned int *len)
> +{
> +    char *path = NULL, *value = NULL;
> +
> +    path = xenstore_vm_key_path(domid, key);
> +    if (!path)
> +        return NULL;
> +
> +    value = xs_read(xenstore, XBT_NULL, path, len);
> +    if (value == NULL) {
> +        fprintf(stderr, "xs_read(%s): read error\n", path);
> +    }
> +
> +    free(path);
> +    return value;
> +}
> +
> +int xenstore_vm_write(int domid, const char *key, const char *value)
> +{
> +    char *path = NULL;
> +    int rc = -1;
> +
> +    path = xenstore_vm_key_path(domid, key);
> +    if (!path)
> +        return 0;
> +
> +    rc = xs_write(xenstore, XBT_NULL, path, value, strlen(value));
> +    if (rc == 0) {
> +        fprintf(stderr, "xs_write(%s, %s): write error\n", path, key);
> +    }
> +
> +    free(path);
> +    return rc;
> +}
> +
> +void xenstore_record_dm(const char *subpath, const char *state)
> +{
> +    char *path = NULL;
> +
> +    if (asprintf(&path,
> +                 "/local/domain/0/device-model/%u/%s", xen_domid, subpath) == -1) {
> +        fprintf(stderr, "out of memory recording dm\n");
> +        goto out;
> +    }
> +    if (!xs_write(xenstore, XBT_NULL, path, state, strlen(state)))
> +        fprintf(stderr, "error recording dm\n");
> +
> +out:
> +    free(path);
> +}
> +
> +void xenstore_record_dm_state(const char *state)
> +{
> +    xenstore_record_dm("state", state);
> +}
> diff --git a/target-xen/xenstore.h b/target-xen/xenstore.h
> index 90baf79..c8144ea 100644
> --- a/target-xen/xenstore.h
> +++ b/target-xen/xenstore.h
> @@ -3,4 +3,10 @@
>
>   int xen_dm_init(void);
>
> +char *xenstore_vm_read(int domid, const char *key, unsigned int *len);
> +int xenstore_vm_write(int domid, const char *key, const char *value);
> +
> +void xenstore_record_dm(const char *subpath, const char *state);
> +void xenstore_record_dm_state(const char *state);
> +
>   #endif /* !XENSTORE_H_ */
>